The present invention relates to a damper for reducing noise, vibration, and harshness issues associated with torque transferring assemblies, such as vehicle driveshafts and propshafts.
Torque transferring assemblies are widely used in vehicles to transfer torque between the engine and the wheels. Typically a torque transferring assembly is arranged between a transmission and an axle assembly, a power transfer unit and an axle assembly, or a transfer case and an axle assembly. To reduce weight, torque transferring assemblies typically include a tubular shaft spanning between a source of rotational energy and the axle assembly. Tubular shafts transmit and amplify vibration and noises from the engine, axle assembly, transmission, transfer case, and wheels. Yet another problem with tubular shafts in torque transferring assemblies is that they produce undesirable noise when rocks or other debris forcefully impact the tubular shaft during vehicle operation.
Some manufacturers have attempted to overcome impact related noises by inserting rigid corrugated cardboard liners into the tubular shaft. The corrugated cardboard liners generally engage the inner wall of the tubular shaft in a press fit relationship to prevent movement of the liner and to dampen impact related noises. These cardboard liners generally do not reduce structural or airborne noise and vibration. In some cases, the corrugated cardboard liners also include rubber stoppers or rubber seals to prevent movement of the corrugated cardboard liner relative to the tubular shaft and thereby prevent noise and vibration caused by movement of the liner relative to the tubular shaft. While these stiff corrugated liners provide generally acceptable reduction in impact related noises, they generally provide minimal reduction in noises or vibrations produced or transmitted by the torque transferring assembly during operation. Another problem with most corrugated liners is that they cannot be combined with most internal dampers that reduce noise and vibration produced or transmitted by the torque transferring assembly.
To address the production or transmission of noises by the torque transferring assembly, other manufacturers have used plugs or other internal dampers inserted at specific nodes within the tubular shaft to reduce specific frequencies of noise and vibration based on damping capability limitations. These plugs typically reduce only a narrow band of frequencies are expensive and require increased assembly time to ensure correct installation at the specific node. Some internal dampers are heavy, thereby mitigating the weight saving benefits of the tubular shaft. Another problem with these plugs or internal dampers is that they generally are not capable of reducing impact noise.
Other manufacturers have also inserted foam, steel wool, cotton, or other materials into the length of the tubular shaft to act as a damper for both impact noise and other noise and vibration issues. While these materials span the length of the tubular shaft to provide dampening against impact noises, they do not reduce noise and vibrations produced or transmitted over a wide enough range of frequencies to an acceptable level.
Therefore, there is a need for a lightweight damper for hollow torque transferring assemblies that reduces noise and vibration issues over a wide frequency range to an acceptable level, and is cost efficient to produce and assemble.